/*
 * Copyright 2009 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.zxing.pdf417;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.BinaryBitmap;
import com.google.zxing.DecodeHintType;
import com.google.zxing.FormatException;
import com.google.zxing.NotFoundException;
import com.google.zxing.Reader;
import com.google.zxing.Result;
import com.google.zxing.ResultPoint;
import com.google.zxing.common.BitMatrix;
import com.google.zxing.common.DecoderResult;
import com.google.zxing.common.DetectorResult;
import com.google.zxing.pdf417.decoder.Decoder;
import com.google.zxing.pdf417.detector.Detector;

import java.util.Map;

/**
 * This implementation can detect and decode PDF417 codes in an image.
 *
 * @author SITA Lab (kevin.osullivan@sita.aero)
 */
public final class PDF417Reader implements Reader {

    private static final ResultPoint[] NO_POINTS = new ResultPoint[0];

    private final Decoder decoder = new Decoder();

    /**
     * Locates and decodes a PDF417 code in an image.
     *
     * @return a String representing the content encoded by the PDF417 code
     * @throws NotFoundException if a PDF417 code cannot be found,
     * @throws FormatException   if a PDF417 cannot be decoded
     */
    @Override
    public Result decode(BinaryBitmap image) throws NotFoundException, FormatException {
        return decode(image, null);
    }

    @Override
    public Result decode(BinaryBitmap image,
                         Map<DecodeHintType, ?> hints) throws NotFoundException, FormatException {
        DecoderResult decoderResult;
        ResultPoint[] points;
        if (hints != null && hints.containsKey(DecodeHintType.PURE_BARCODE)) {
            BitMatrix bits = extractPureBits(image.getBlackMatrix());
            decoderResult = decoder.decode(bits);
            points = NO_POINTS;
        } else {
            DetectorResult detectorResult = new Detector(image).detect();
            decoderResult = decoder.decode(detectorResult.getBits());
            points = detectorResult.getPoints();
        }
        return new Result(decoderResult.getText(), decoderResult.getRawBytes(), points,
                BarcodeFormat.PDF_417);
    }

    @Override
    public void reset() {
        // do nothing
    }

    /**
     * This method detects a code in a "pure" image -- that is, pure monochrome image
     * which contains only an unrotated, unskewed, image of a code, with some white border
     * around it. This is a specialized method that works exceptionally fast in this special
     * case.
     *
     * @see com.google.zxing.qrcode.QRCodeReader#extractPureBits(BitMatrix)
     * @see com.google.zxing.datamatrix.DataMatrixReader#extractPureBits(BitMatrix)
     */
    private static BitMatrix extractPureBits(BitMatrix image) throws NotFoundException {

        int[] leftTopBlack = image.getTopLeftOnBit();
        int[] rightBottomBlack = image.getBottomRightOnBit();
        if (leftTopBlack == null || rightBottomBlack == null) {
            throw NotFoundException.getNotFoundInstance();
        }

        int moduleSize = moduleSize(leftTopBlack, image);

        int top = leftTopBlack[1];
        int bottom = rightBottomBlack[1];
        int left = findPatternStart(leftTopBlack[0], top, image);
        int right = findPatternEnd(leftTopBlack[0], top, image);

        int matrixWidth = (right - left + 1) / moduleSize;
        int matrixHeight = (bottom - top + 1) / moduleSize;
        if (matrixWidth <= 0 || matrixHeight <= 0) {
            throw NotFoundException.getNotFoundInstance();
        }

        // Push in the "border" by half the module width so that we start
        // sampling in the middle of the module. Just in case the image is a
        // little off, this will help recover.
        int nudge = moduleSize >> 1;
        top += nudge;
        left += nudge;

        // Now just read off the bits
        BitMatrix bits = new BitMatrix(matrixWidth, matrixHeight);
        for (int y = 0; y < matrixHeight; y++) {
            int iOffset = top + y * moduleSize;
            for (int x = 0; x < matrixWidth; x++) {
                if (image.get(left + x * moduleSize, iOffset)) {
                    bits.set(x, y);
                }
            }
        }
        return bits;
    }

    private static int moduleSize(int[] leftTopBlack, BitMatrix image) throws NotFoundException {
        int x = leftTopBlack[0];
        int y = leftTopBlack[1];
        int width = image.getWidth();
        while (x < width && image.get(x, y)) {
            x++;
        }
        if (x == width) {
            throw NotFoundException.getNotFoundInstance();
        }

        int moduleSize = (x - leftTopBlack[0]) >>> 3; // We've crossed left first bar, which is 8x
        if (moduleSize == 0) {
            throw NotFoundException.getNotFoundInstance();
        }

        return moduleSize;
    }

    private static int findPatternStart(int x, int y, BitMatrix image) throws NotFoundException {
        int width = image.getWidth();
        int start = x;
        // start should be on black
        int transitions = 0;
        boolean black = true;
        while (start < width - 1 && transitions < 8) {
            start++;
            boolean newBlack = image.get(start, y);
            if (black != newBlack) {
                transitions++;
            }
            black = newBlack;
        }
        if (start == width - 1) {
            throw NotFoundException.getNotFoundInstance();
        }
        return start;
    }

    private static int findPatternEnd(int x, int y, BitMatrix image) throws NotFoundException {
        int width = image.getWidth();
        int end = width - 1;
        // end should be on black
        while (end > x && !image.get(end, y)) {
            end--;
        }
        int transitions = 0;
        boolean black = true;
        while (end > x && transitions < 9) {
            end--;
            boolean newBlack = image.get(end, y);
            if (black != newBlack) {
                transitions++;
            }
            black = newBlack;
        }
        if (end == x) {
            throw NotFoundException.getNotFoundInstance();
        }
        return end;
    }

}
